THE BLOOD 



241 



indication that there is a corresponding increase of the total number in the 

 general volume of the blood is uncertain. The following table will show the 

 increase in the count per cubic millimeter at different altitudes: 



This increase in the number of corpuscles takes place, according to 

 Viault's observations, within two or three weeks, and is apparently not con- 

 nected with either diet or mode of life, but rather with diminished atmos- 

 pheric, if not oxygen, pressure. On returning to sea-level there is a gradual 

 reduction, without any apparent destruction of the corpuscles, to their normal 

 number. The reason for these variations is not clear. 



The method of counting corpuscles introduced by Vierordt and Welcker 

 has been modified by different observers, and especially by Thoma. On 



FIG. 94. HEMOCYTOMETER. a, Surface; b, section view; c, squares on the surf ace of B magnified- 

 M, G, S t mouth piece, rubber tube and pipette. 



account of the great number of corpuscles in i cubic millimeter of blood, it 

 becomes necessary for purposes of enumeration that the blood be diluted a 

 definite number of times and that the diluted mixture be placed in a counting 

 chamber possessing a definite capacity. By means of the pipette or milang- 

 eur of Potain and the counting chamber of Thoma both these objects are 

 attained. 



The pipette consists of a capillary tube (Fig. 94) provided with an enlarge- 

 ment containing a freely movable small glass ball, E. One end of the tube, S, 

 is pointed, while to the other end is attached a rubber tube, G, for the purpose 

 of facilitating the introduction of the blood and the diluting fluid. The capillary 

 tube, which is accurately calibrated, carries marks, 0.5, i, 101, which signify that 

 if the tube be filled with blood up to the mark i and the diluting fluid be 

 16 



